Eating style, overeating and weight gain. A prospective 2-year follow-up study in a representative Dutch sample

Appetite 59 (2012) 782–789

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Eating style, overeating and weight gain. A prospective 2-year follow-up study in a representative Dutch sample q Tatjana van Strien a,⇑, C. Peter Herman b, Marieke W. Verheijden c a

Department of Clinical Psychology, Institute for Gender Studies and Behavioral Science Institute, Radboud University Nijmegen, P.O. Box 9104, 6500 HE Nijmegen, The Netherlands Department of Psychology, University of Toronto, Ontario, Canada M55 3G3 c TNO, Leiden, The Netherlands b

a r t i c l e

i n f o

Article history: Received 20 February 2012 Received in revised form 7 August 2012 Accepted 12 August 2012 Available online 20 August 2012 Keywords: Dietary restraint Emotional eating External eating Physical activity Overeating Body mass change

a b s t r a c t This study examined which individuals are particularly at risk for developing overweight and whether there are behavioral lifestyle factors that may attenuate this susceptibility. A prospective study with a 2-year follow-up was conducted in a sample representative of the general population of The Netherlands (n = 590). Body mass change (self-reported) was assessed in relation to overeating and change in physical activity (both self-reported), dietary restraint, emotional eating, and external eating, as assessed by the Dutch Eating Behavior Questionnaire. There was a consistent main (suppressive) effect of increased physical activity on BMI change. Only emotional eating and external eating moderated the relation between overeating and body mass change. However, the interaction effect of external eating became borderline significant with Yes or No meaningful weight gain (weight gain >3%) as dependent variable. It was concluded that whilst increasing physical activity may attenuate weight gain, particularly high emotional eaters seem at risk for developing overweight, because overconsumption seems to be more strongly related to weight gain in people with high degrees of emotional eating. Ó 2012 Elsevier Ltd. All rights reserved.

The current environment has been described as obesogenic (Swinburn, Egger, & Raza, 1999), meaning that abundant availability of food, coupled with declines in physical activity in interaction with genetic susceptibility, encourage positive energy balance, weight gain, and ultimately overweight. Despite the potency of this obesogenic environment, not all people become overweight; some remain lean. Susceptibility to increased body weight may be understood at many levels, ranging from genetic, physiological or metabolic, to behavioral and psychological (Blundell et al., 2005). The present study focuses on behavioral and psychological factors, and examines which individuals are particularly at risk for developing overweight and whether there are behavioral lifestyle factors that may exacerbate or attenuate this susceptibility. Increasing physical activity and reducing food intake (dieting) are considered cornerstones in the prevention and treatment of obesity (Holmes, Ekkekakis, & Eisenmann, 2010; Keith et al.,

2006). Yet dietary restraint1 has been found to be associated with excessive food intake and weight gain (Chaput et al., 2009; Polivy & Herman, 1985; Stice, Cameron, Killen, Hayward, & Taylor, 1999). Also reviews of calorie-restricted diets have not provided grounds for optimism regarding the effectiveness of such diets in the long term (Aphramor, 2010; Mann et al., 2007). In the Mann et al. (2007) meta-analysis, between one-third and two-thirds of the dieters had at follow-up regained more weight than they lost on their diets. A problem with dietary restraint is that the body cannot distinguish true food shortage from self-imposed food restriction and acts as if it is in the starvation mode: feelings of hunger increase and metabolic rate slows down (anabolism and adaptive thermogenesis) (Goldsmith et al., 2010; Major, Doucet, Trayhurn, Astrup, & Tremblay, 2007). Moreover, dietary restraint (a form of inhibition) is often associated with overeating tendencies (disinhibition), as in emotional eating or external eating. Emotional eating refers to the tendency to overeat in response to negative emotions as result from poor interoceptive awareness, a notion derived from Bruch’s (1964), psychosomatic theory of obesity. External eating refers to the overeating tendency resulting from susceptibility to tempting

q Acknowledgements: We thank The Netherlands Nutrition Centre for allowing secondary data analysis and the Dutch Ministry of Health, Welfare and Sports for funding Marieke W. Verheijden. ⇑ Corresponding author. E-mail address: [email protected] (T. van Strien).

1 Dietary restraint is defined as the attempted restriction of food intake in order to maintain or loose body weight. Although dietary restraint or ‘dieting’ is not the same as ‘being on a diet’, a dichotomous category that can be answered with a Yes or a No, the question ‘Do you diet’ was found to load on the same factor as dietary restraint (see further, Van Strien, Herman, Engels, Larsen, & Van Leeuwe, 2007).

Introduction

0195-6663/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.appet.2012.08.009

T. van Strien et al. / Appetite 59 (2012) 782–789

food cues, a notion derived from Schachter’s (1968) externality theory of obesity (Herman & Polivy, 2008). Emotional and/or external eating can therefore complicate the association between dietary restraint, food intake, and change in body weight. What ought to produce weight loss may end up producing weight gain (Herman, van Strien, & Polivy, 2008). The precise direction of the relationship between dietary restraint and these overeating tendencies is as yet unclear and may even differ for various subgroups (Spoor et al., 2006; Stice, 1998; Stice, Presnell, & Sprangler, 2002; van Strien, Engels, van Leeuwe, & Snoek, 2005). The risk of anabolism and weight (re)gain after a diet may be counteracted by increasing physical activity. What is more, physical activity may have benefits that go beyond increased caloric expenditure and increasing metabolic rate, because it has been found to be associated with lower depressive symptomatology, decreased feelings of tension, and greater emotional well-being (Amenesi & Whitaker, 2008; Dunn, Trevedi, Kampert, Clark, & Chambliss, 2005). Physical activity was found to be negatively associated with emotional and external eating (van Strien & Koenders, 2010), and physical activity self-efficacy (i.e., confidence in one’s ability to be regularly physically active) was also negatively associated with emotional eating (Konttinen, Silventoinen, Sarlio-Lähteenkorva, Männistö, & Haukkala, 2010). For the present study we were interested in extending prospectively earlier cross-sectional results regarding the moderator effects of restrained, emotional, and external eating on the relation between overconsumption and overweight. In this earlier study in a representative Dutch sample (van Strien, Herman, & Verheijden, 2009), both dietary restraint and emotional overeating significantly moderated the relationship between overconsumption and level of overweight. Overconsumption was more strongly related to overweight in people with lower levels of dietary restraint and in people with higher levels of emotional eating. External eating, however, did not moderate the relationship between overconsumption and level of overweight, and there also was no positive main effect of external eating on level of overweight. It was concluded that one’s body weight is possibly determined more by one’s tendency toward emotional eating than by one’s sensitivity to environmental food cues. A further conclusion was that dietary restraint may prevent people who overeat from developing overweight. The finding that overweight people did not differ from normalweight people in their degree of external eating is somewhat surprising in view of the recent interest in the possible role of environmental (external) food cues in the development of overweight (the obesogenic environment!) (Herman & Polivy, 2008). The absence of a difference between overweight and normal weight people in external eating is, however, consistent with similar results in various other studies (Lluch, Herbeth, Mëjean & Siest, 2000; Pothos, Tapper, & Calitri, 2009; Snoek, van Strien, Janssen & Engels, 2007; van Strien, Herman, et al., 2007; Wardle, 1987; Wardle et al., 1992). Also in a prospective 4-year follow-up study on 1576 adult Korean twins and their families, there was no support for external eating as risk factor for development of overweight; external eating was not associated with either overweight or weight gain (Sung, Lee, & Song, 2009). The same result was obtained in a prospective 2-year follow-up study on 1562 employees in a Dutch banking environment (Koenders & van Strien, 2011). So the question now arises: Is the absence of support for external eating as a risk factor for overweight and weight gain robust and can this finding be replicated in a prospective study in a different representative Dutch sample? The finding by van Strien et al. (2009) that dietary restraint attenuated the relation between overconsumption and overweight is also in need of replication in a prospective study, because it conflicts with outcomes of earlier studies in which dietary restraint

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was shown to be an important risk-factor for overeating and weight gain (Mann et al., 2007; Polivy & Herman, 1985). Also of interest would be the assessment of the possible attenuating role of physical activity in the development of overweight. Results of a recent meta-analysis of diet interventions suggested that the risk of regaining body weight was lower in a diet-plus-exercise intervention than in a diet-alone intervention (Wu, Gao, Chen, & van Dam, 2009). Further, in the prospective 2-year follow-up study in Dutch banking employees, a high level of athletics was found to be predictive of weight loss. A further finding in that study was that the positive association of emotional eating with weight gain was weaker in employees with high engagement in sports than in those with low engagement in sports (Koenders & van Strien, 2011). Accordingly, it would be of interest to ascertain whether physical activity has an attenuating effect on the association between over-consumption and weight gain. In the present prospective study on a representative Dutch sample, overconsumption, dietary restraint, emotional eating, external eating, and physical activity were assessed in spring 2009 (T1) and tested against BMI in spring 2011 (T2), controlling for spring 2009 (T1) BMI. The following hypotheses were formulated. Dietary restraint and physical activity were both expected to attenuate the positive relationship between overeating and body mass change after 2 years, whereas emotional eating was expected to strengthen this relationship. No moderator effect was expected for external eating. We further expected these findings to remain robust in the models that included the other eating styles as possible confounders. Methods Participants Data were collected in a cohort of Dutch adults (representative for age, sex, SES, ethnic origin, and region in The Netherlands) as part of a larger longitudinal study on knowledge and use of the Dutch mass media campaign: Monitoring Healthy body weight. Participants were recruited through a panel service agency. At baseline, a sample of 1200 participants was recruited. At the first measurement (T1) of the present study, height and weight measures were available for 744 participants (64% of the people who had been initially approached to participate). Fortyeight percent of the participants were female. Educational levels broke down into 32.9% lower-level education, 42.2% medium-level education, and 24.9% higher-level education. Further, 17.6% of the participants were non-Dutch and the mean age was 48.2 years (SD = 14.5; range: 19–75 years). A total 14.7% lived in the three big cities and their agglomeration, 27.5% lived in the West, 10.6% in the North, 21.6% in the East and 25.4% in the South part of the Netherlands. These distributions are in close correspondence to the actual distribution in the Dutch population according to CBS (Central Bureau voor de Statistiek [Central Office for Statistics]) (2009). The only exception is educational levels, where the actual distributions for people with ages between 45 and 65 years in the age-lower-level, medium-level and higher-level education are, respectively, 34%, 38% and 27%. Compared to the first measurement, 154 participants (21.6%) at the second measurement (T2) had missing weight and height measures. There were no differences between the drop-outs and nondropouts in regard to their BMI, ethnicity (Dutch versus non-Dutch), education and sex. However, the mean age was lower for the dropouts compared to the non-dropouts, t(742) = 4.477, p<.001. So, in the present study, complete information was obtained from 590 participants, 308 males and 282 females (see Table 3 for the mean (SD) of the participants’ age and BMI). When categorizing participants according to weight loss of >3%, weight maintenance (±3%), or weight gain of >3% of baseline weight (see for this

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definition of weight maintenance: Stevens, Trueskale, McClain, & Cai, 2006), we found that between T1 and T2 a total of 16.4% had lost weight (with a mean weight loss of .89 kg (SD = 2.6)), 52.2% showed weight maintenance, and 31.1% showed weight gain (with a mean weight gain of .87 kg (SD = 2.9)). Procedure Data were collected either online or using paper and pencil in a so called ‘‘food and health’’ study. Measurements took place in November and March of four consecutive years, starting in November 2007. The present study started in Spring 2009 (T1), because the three eating styles (all of them measured only once) had been measured close to this assessment (T1),and ended 2 years later (Spring 2011). Constructs that were measured include: sociodemographics, self-reported height and weight, and behaviors related to energy-balance, including (change in) physical activity and the eating styles dietary restraint, emotional eating, and external eating. Measures Body mass index (BMI) was calculated as weight (kg) divided by height (m) squared (self-reported). Emotional, external, and restrained eating were measured with the Dutch Eating Behavior Questionnaire (DEBQ, van Strien, Frijters, Bergers, & Defares, 1986). The DEBQ has 33 items forming three separate scales: emotional eating (13 items: e.g. ‘‘Do you have a desire to eat when you are irritated?’’), external eating (10 items: e.g. ‘‘If food smell and looks good, do you eat more than usual?’’) and restrained eating (10 items: e.g. ‘‘Do you try to eat less at mealtimes than you would like to eat?’’). Each of the scales has displayed good internal consistency, factorial and predictive validity (van Strien, Herman, et al., 2007; van Strien, Herman, & Anschutz, 2012; van Strien & van de Laar, 2008; van Strien, Herman, Anschutz, Engels, & de Weerth, 2012). The reliabilities (Cronbach’s alpha) for the present study were .96, .85, and .93, respectively. Physical activity: Time spend doing physical activity, in summer and winter, was translated to the Dutch norm for Healthy Physical activity (Haskell et al., 2007; Pollock et al., 1998) To comply with the norm, a person has to be active at least 5 days per week in summer and winter for more than 30 min, doing cycling, walking, sporting or comparable moderately or intensive physical activities. The resulting physical activity levels broke down into ‘‘not norm active’’ (less than five physical activities in summer and winter) and ‘‘norm active’’ (at least five physical activities per week in summer and winter). Overconsumption was measured with the question: ‘‘Can you indicate how often you eat or drink somewhat too much’’: (1) never. . .. (6) more than twice a week.2 Subjects were classified as being low versus high overconsumers if they reported overconsuming less than once a month versus once a month or more, which corresponded to the median split of responses to this question (van Strien et al., 2009). Data-analysis All variables were inspected for skewness and no problems were observed. Next, descriptive analyses were conducted to gather information about means, standard deviations, and inter-correlation of the variables. The differences in the means according to baseline overconsumption and overweight status (normal 2 Although we were not specifically interested in drinking, intake of sugarsweetened beverages and alcohol is highly caloric, so overindulgence in sugarsweetened beverages and/or alcohol may be equivalent to overeating in terms of its effect on body weight.

weight = 0 (BMI < 25); overweight = 1 (BMI P 25)) of the scores on restrained eating, emotional eating, external eating, age, and education were measured with an independent t-test, and effect sizes were also included. Associations of physical activity (notnormactive versus norm-active) and sex with overconsumption and overweight status were determined with chi-square tests and the percentage of norm-active and males according to overconsumption/overweight status are also reported. Owing to the numerous t-tests and correlations conducted, we report only those t-tests and correlations significant at the 1% level. Four hierarchical regression analyses were performed to examine the possible moderator effects of restrained eating, emotional eating, external eating and physical activity respectively, on the relationship between overeating and weight change (BMI at T2 corrected for BMI at T1). In the first step we corrected for age, sex, and education. Because of the high interrelation between emotional eating, external eating, and dietary restraint (see Table 3), we corrected in subsequent analyses in the third step (after the step on the main effects of each of the eating styles, overeating, and physical activity) for the other eating styles. The predictor variables in the various (four) steps of the full model are shown in Table 4. To avoid multicollinearity in the regression analyses, all variables were centered before computing interaction terms. P values <.05 (two-tailed) were considered statistically significant. Results Mean differences Means and standard deviations of all variables may be found in Table 1 (low versus high overconsumers at base line) and Table 2 (normal-weight and overweight participants at baseline). There were no differences between high and low overconsumers in regard to age and sex. On all other variables the means of high overconsumers were significantly higher on all variables than those of low overconsumers (see Table 1), except for physical activity, where percentage of norm-active participants was significantly lower. The higher means on emotional and external eating may be interpreted as supporting the validity of the measure for overconsumption. As shown in Table 2, the means of overweight participants were also higher than of normal-weight participants on all variables, except for sex and education, where there were no differences, and for physical activity, where the percentage of norm-active participants was significantly lower. The effect sizes (d) indicated only small effects, with the exception of restrained eating where the effect size was large. Pearson correlations Table 3 presents the Pearson correlation coefficients between all the variables in the present study. Of special interest for our purposes are the correlations between BMI change and the BMI at T1 and at T2 and the measures for overeating (overconsumption, emotional and external eating) and for dietary restraint and physical activity. Overconsumption, dietary restraint, emotional eating, external eating and physical activity all showed significant, though moderate (r < .30) correlations with BMI at T1 and BMI at T2, but only emotional eating showed a significant correlation with BMI change (calculated by regressing BMI at T2 (dependent variable) on BMI at T1 (standardized residual). Also, change in overconsumption (overconsumption at T2, controlled for overconsumption at T1) was not significantly associated with change in BMI (r = .075; p = .068, see Table 3, footnote b), so we decided to use overconsumption at T1 and not change in overconsumption in

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T. van Strien et al. / Appetite 59 (2012) 782–789 Table 1 Means, standard deviations and t-test for the sub-samples with low versus high overconsumption at baseline.

BMI DEBQ-R DEBQ-em DEBQ-ex % Norm-active Age % Males Educationb

Low overconsumption (n = 295)

High overconsumption (n = 295)

Difference

Mean

Mean

T

p

4.312 8.265 7.366 6.861 13.856c .816 1.85c 2.767

<.001 <.001 <.001 <.01 <.001 0.415 0.174 <.01

26.47 2.46 1.91 2.43 43.1 47.56 54.9 1.80

SD 4.21 0.86 0.73 0.55 15.37 0.72

SD

27.01 3.01 2.36 2.73 28.3 48.53 49.3 1.97

4.45 0.72 0.77 0.53 13.56 0.77

da 0.12 0.69 0.60 0.55 0.07 0.23

a

d = effect size by Cohen’s d (0.20 = small, 0.50 = medium, 0.80 = large). b Lower education (primary school, lower vocational education or lower general secondary education) = 1; medium education (intermediate vocational education, higher general secondary education, or pre-university education = 2; higher education (higher vocational education or academic training) = 3. c Chi-square test.

Table 2 Means, standard deviations and t-test for the sub-samples of normal-weight and overweight people at baseline. Normal weight N = 252 Mean Overeating DEBQ-R DEBQ-em DEBQ-ex % Norm-active Age % Males Educationb

0.40 2.48 1.99 2.49 44.8 45.57 47.6 1.91

Overweight N = 338 SD 0.49 0.87 0.73 0.57 15.18 0.76

Mean 0.57 2.93 2.24 2.65 28.9 49.89 55.6 1.86

Difference SD 0.49 0.76 0.81 0.54 13.68 0.74

T

p

3.44 6.52 3.82 3.33 15.78* 3.57 3.705* .707

<.001 <.001 <.001 <.01 <.001 <.001 .054 .44

da 0.35 0.81 0.32 0.29 0.30 0.07

a

d = effect size by Cohen’s d (0.20 = small, 0.50 = medium, 0.80 = large). b Lower education (primary school, lower vocational education, or lower general secondary education) = 1; medium education (intermediate vocational education, higher general secondary education, or pre-university education = 2; higher education (higher vocational education or academic training) = 3. * Chi-Square-test.

our regression models (see below). However, change in physical activity, which was calculated by regressing physical activity at T2 (dependent variable) on physical activity at T1 (standardized residual), showed a significant negative correlation with change in BMI (r = .13), so we decided to use change in physical activity instead of physical activity at T1 in our regression models. (Dietary restraint was measured only once (close to T1), so correlations of increases in dietary restraint with BMI change could not be calculated.) Hierarchical regression analyses BMI at T1 was significantly related to BMI at T2, but there were no main effects for age, sex, or education (Table 4, step 1). In the model testing the moderator effect of dietary restraint, there was a main effect of increase in physical activity (B = .195, p = .002). There was, however, no main effect for overeating or dietary restraint at step 2, and there also was no moderator effect of dietary restraint on the relation between overconsumption and weight change (ps > .120)(not shown), and this remained so in the model where we additionally controlled for emotional and external eating in step 3 (see Table 4). In the model testing the moderator effect of emotional eating, there were only main effects for increases in physical activity (B = .202, p = .001) and emotional eating (B = .179, p = .044). There also was a moderator effect of emotional eating on the relationship between overeating and BMI change (B = .424, p = .011) (not shown), and this remained so when we also controlled for external eating and dietary restraint (see Table 4). In the model testing the moderator effect of external eating, there was a main effect only for increases in physical activity (B = .060, p = .034).There also was a moderator effect of

external eating on the relationship between overeating and weight change (B = .226, p = .030) (not shown), and this effect remained when we controlled for emotional eating and dietary restraint (see Table 4). It should be noted that in this model the main effect of emotional eating disappeared when we controlled for external and restrained eating (which are highly correlated with emotional eating). In the model testing the moderator effect of increases in physical activity, there was only a main effect for increases in physical activity (B = .198, p = .002). There was no moderator effect of increases in physical activity on the relationship between overeating and weight change (B = .121, p = .334), and this remained so when we also controlled for emotional eating, external eating, and dietary restraint (see Table 4). The R2 associated with the full model testing the moderator effect of dietary restraint, emotional eating, external eating and increased physical activity was, respectively, .890, .892, .891 and .890. As recommended by Holmbeck (2002), post hoc analyses on the simple model were conducted to determine the nature of the significant interactions. Prior to these analyses, we created a highemotional eating (i.e., centered emotional eating – 1 SD) and low-emotional eating variable (i.e., centered emotional eating + 1 SD) Each of these variables was then multiplied by the (centered) overconsumption variable to create interaction terms. With these variables, we conducted two regression analyses, each of which included the main effect for overconsumption, one of the conditional emotional eating variables (high emotional eating or low emotional eating), and the interaction of the overconsumption and emotional eating variable, thereby producing the slope for the high- and low-emotional eating conditions. Results of the regression for high emotional eating indicated that degree of overconsumption had a significant positive association with weight gain,

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Table 3 Pearson correlation coefficients.

1. BMI-changea 2. BMI T1 3. BMI T2 4. Over-consumptionb 5. DEBQ-R 6. DEBQ-em 7. DEBQ-ex 8. Physical activity 9. Increases in physical activity 10. Age 11. Sex 12. Educationc Mean SD

1

2

3

.15* .47* .05 .08 .11* .09 .04 .13* .02 .01 .01 .02 1.01

.94* .18* .27* .20* .13* .16* .03 .12* .02 .04 26.24 4.40

.17* .27* .22* .15* .15* .07 .10 .01 .42 26.53 4.52

4

.32* .29* .27* .15* .02 .03 .06 .11 .50 .50

5

6

7

.37* .13* .12* .04 .19* .24* .05 2.73 .84

.60* .09 .01 .19* .24* .08 2.13 .78

.11* .03 .30* .10 .12 2.58 .56

8

9

.01 .02 .02 .06 .36 .48

.03 .05 .04 .01 .99

10

11

12

.08 .15 48.06 14.48

.10 .52 .50

1.88 .75

a

BMI change was calculated by regressing BMI at T2 (dependent variable) on BMI at T1 (standardized residual). Change in overconsumption (overconsumption T2 controlled for overconsumption at T1) was also not significantly correlated with change in BMI (BMI at T2 controlled for BMI at T1) (r = .075; p = .068), so we used overconsumption at T1 as measure for overconsumption. c Lower education (primary school, lower vocational education, or lower general secondary education) = 1; medium education (intermediate vocational education, higher general secondary education, or pre-university education = 2; higher education (higher vocational education or academic training) = 3. * p < .01. b

[B] = 0.384, p = 0.043. In contrast, results of the regression for low emotional eating indicated that overconsumption had no significant association with weight change, [B] = .286, p = .120. Further, results of the regression for high external eating indicated that degree of overconsumption had a significant positive association with weight gain, [B] = 0.390, p = 0.037. In contrast, results of the regression for low external eating indicated that overconsumption had no significant association with weight change [B] = .276, p = .134.

Highly similar results were obtained in post-hoc hierarchical regression analyses where we categorized the participants in the present study as non-gainers (weight loss or weight maintenance (63% weight gain, n = 405) versus gainers (weight gain >3%, n = 185) (data not shown). (see for this definition of weight maintenance: Stevens et al., 2006) Specifically: there were no significant moderator effects in the final (full) model for dietary restraint or increased physical activity on the relation between overconsumption and weight change (respectively, B = .061, p = .212 and

Table 4 Effects of individual and joint moderators on the relation between overconsumption and BMI at T2 (B at entry). p

R2 change (p)

.943 .011 .003 .003

.005 .000 .423 .850 .842

.887 (<.001)

.063 .133 .084 .114 .153 .161

.043 .006 .024 .020 .011 .000

.002 .701 .120 .313 .576 .977

.002 (.005)

.202 .040 .179

.063 .132 .089

.045 .004 .031

.001 .765 .044

.003 (.002)

.086 .094 .477

.153 .088 .170

.011 .017 .040

.575 .286 .005

.000 (.501) .001

Moderator effect of external eating 2 Increase in physical activity Overconsumption DEBQ-ex 3 DEBQ-em DEBQ-R 4 DEBQ-ex  overconsumption

.202 .053 .194 .115 .094 .646

.063 .133 .124 .114 .088 .235

.045 .006 .024 .020 .017 .038

.001 .692 .119 .313 .286 .006

.002 (.005)

Moderator effect of increased physical activity 2 Overconsumption Physical activity 3 DEBQ-R DEBQ-em DEBQ-ex 4 Increased physical activity  overconsumption

.109 .198 .094 .115 .086 .112

.128 .063 .088 .114 .153 .125

.012 .044 .017 .020 .011 .012

.396 .002 .286 .313 .575 .371

.002 (.006) .001 (.146)

Step

B

SE

1.307 .968 .004 .024 .017

.464 .014 .004 .126 .085

Moderator effect of dietary restraint 2 Increase in physical activity Overconsumption DEBQ-R 3 DEBQ-em DEBQ-ex 4 DEBQ-R  overconsumption

.195 .055 .131 .115 .086 .005

Moderator effect of emotional eating 2 Increase in physical activity Overconsumption DEBQ-em

1

3 4

Intercept overweight level BMI T1 Age Sex Education

DEBQ-ex DEBQ-R DEBQ-em  overconsumption

Bèta

.001 (.228) .000

.001 (.005) .001

.000

T. van Strien et al. / Appetite 59 (2012) 782–789

B = .003, p = .936). There was a significant moderator effect for emotional eating on the relation between overconsumption and overweight (B = .124, p = .018) but the earlier significant moderator effect of external eating on the relationship between overconsumption and weight change became borderline significant (B = .136, p = .059).

Discussion The present study replicated an earlier cross-sectional study (van Strien et al., 2009) in a representative Dutch sample this time using a prospective 2-year follow-up design. In addition to overconsumption, emotional eating, external eating, and dietary restraint, physical activity was also assessed. As in the earlier study, high overconsumers differed from low overconsumers in that they were more often overweight, had higher degrees of dietary restraint, emotional eating and external eating, and were better educated. A further finding was that they engaged less often in physical activity, but, unlike the earlier study, there was no sex difference between low and high overconsumers. Most of these factors were connected to overweight, but the effect size of the difference between overweight people and their normal-weight counterparts was, with the exception of restrained eating, generally small. The absence of a difference in their degree of external eating in the earlier van Strien et al., 2009 study was, thus, not found in the present study. But as in the earlier study there was no sex difference or difference in education between normal-weight and overweight people, and also in the present study overweight people were older than their normal weight counterparts. Overconsumption and external eating were not associated with BMI change. The absence of a main effect of external eating on BMI change is in line with results of earlier prospective studies (Koenders & van Strien, 2011; Sung et al., 2009). So the present finding adds to the accumulating evidence that external eating may not be a good a good predictor of BMI change. A further finding was that the significant main effect of emotional eating on BMI change disappeared when we controlled for restrained eating and external eating. This means that the present study did not replicate the findings of the South Korean Healthy Twin study, where emotional eating (along with high restrained eating) was found to be an indicator for long-term (4-year follow-up) weight gain in 1576 adult twins and their families (Sung et al., 2009). It also did not replicate the main effect of emotional eating on change in BMI of the prospective 2-year follow up study in 1562 employees in a Dutch banking environment (Koenders & van Strien, 2011). One difference between that banking study and the present one is that eating styles in the banking study were assessed in Autumn 2008, right in the middle of the credit crises, which may have evoked in the employees of the Dutch bank precisely that sort of unlabeled uncontrollable anxiety implicated in emotional eating (Bruch, 1964; Slochower, 1983). In contrast, the present study started in Spring 2009 in a representative Dutch sample in the general population in the Netherlands. Relatively few people were directly affected by the aftermath of the 2008 credit crises. Earlier (van Strien, Rookus, Bergers, Frijters, & Defares, 1986) it was shown that emotional eating is associated with prospective weight gain only in interaction with negative life events, but negative life events were not assessed in the present study. There was no clear support for restrained eating as risk factor for weight gain (see also, de Lauzon-Guillain et al., 2006; Koenders & van Strien, 2011; van Strien, Van de Lear, et al., 2007). Nevertheless, restrained eating was clearly not associated with weight loss either, although it may be necessary for dietary restraint to

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increase over time if one is to lose weight in the long run (Drapeau et al., 2003). Dietary restraint was assessed once, at baseline, in the present study, so it was not possible to assess the association of increases in dietary restraint with follow-up weight change. Increased physical activity showed a consistent main (suppressive) effect on BMI change. The finding that only increases in physical activity and not physical activity at baseline were associated with weight loss is consistent with evidence that higher physical activity may be needed to achieve weight loss (Tate, Jeffery, Sherwood, & Wing, 2007). It may, however, be difficult to maintain these higher levels of activity, and a finding of concern in the study by Tate et al. (2007) was that none of the levels of activity that had been attained in that study had been entirely effective in preventing subsequent weight regain. In view of this concern, the consistent main effect of increased physical activity on subsequent weight loss after 2 years in the present study is quite remarkable. It is worth noting that these selfreported increases in physical activity were not associated with an explicit physical activity intervention. Perhaps self-generated physical activity increases are more enduring than are imposed interventions. Also in the prospective study, emotional eating moderated the relationship between overconsumption and body weight change. Unlike the earlier cross-sectional study, there was no moderator effect for restrained eating, but there was a significant moderator effect for external eating. Overconsumption seemed to be more strongly related to overweight in people with higher levels of emotional or external eating. The moderator effect for emotional eating remained significant when the participants were categorized as people with no meaningful weight gain versus people with meaningful weight gain, and the moderator effect for external eating became borderline significant. The replication of the earlier significant moderator effect of emotional eating on the relationship between overconsumption and overweight in the present prospective study is in line with recognitions that diet and physical activity leave a considerable amount of variance unexplained (Keith et al., 2006; Tremblay & Chaput, 2008) and that one of the other possible roads to obesity may be paved with stress (Holmes et al., 2010). In this respect it should be noted that stress can be associated with both undereating/weight loss and overeating/weight gain (Gold & Chrousos, 2002). In fact, undereating and weight loss are the typical and evolutionary adaptive responses to stress, whereas overeating and weight gain are the atypical responses (Gold & Chrousos, 2002). Emotional eating may be the outcome of early learning experiences where there was insufficient regard for the child’s real needs or adverse parenting early in life (Bruch, 1964). It was found to emerge in adolescence in association with depressive feelings and inadequate parenting, such as psychological control and punishing without any justification – in interaction with a genetic vulnerability (Snoek, Engels, Janssens, & van Strien, 2007; Topham et al., 2011; van Strien, Snoek, van der Zwaluw, & Engels, 2010; van Strien, Van der Zwaluw, & Engels, 2010). In the present study, people who combined overconsumption with a high tendency toward emotional eating showed weight gain, whereas no association with weight gain was found in people who combined overconsumption with low tendency toward emotional eating. A possible explanation for this finding may lie in differences between high and low emotional eaters in the type and energy density of the foods that they overconsume. Previously it has been shown that high emotional eaters consume significantly more sweet high-fat foods and more energy dense foods in response to stress than do low emotional eaters (O’Connor, Jones, Conner, McMillan, & Ferguson, 2008; Oliver, Wardle, & Gibson, 2000). (See also the study by van Strien, Hermen et al., 2012, in which high emotional eaters consumed more buttercake than did

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low emotional eaters in the ego-threat condition (see footnote 7 on page 283)).3 A further outcome in the earlier van Strien et al., 2009 study was that there had been a substantial increase in emotional eating between 1983 and 2006, but that this increase was not paralleled by a similar large increase in external eating (see the Discussion section, p.385, van Strien et al., 2009). Does this also hold true for the present representative Dutch sample? A total of 804 respondents had filled in the DEBQ at Time 1, but the scores on emotional eating were only little higher (mean = 2.19; SD = .78) than those that had been obtained in 1983 in a different but also representative Dutch sample (so called Ede sample) (mean = 1.92; SD = .68) (see van Strien et al., 1986, Table 3). The effect size was 0.27, indicating only a small effect. However, the mean age of the present sample was 48.05 (SD = 14.48), which is substantially higher than those of the three age groups in the Ede sample (21– 23, 26–28 and 31–33 years as of 1 January 1983). In the current subsample of participants with ages 640 years (n = 249), substantially higher emotional eating scores were obtained: 2.37 (SD = .80), and the effect size of the difference with scores in the Ede sample was 0.68, indicating a medium effect. In regard to external eating and restrained eating, the following findings were obtained: The current scores on external eating in the total sample and the subsample with ages 640 years, respectively, were 2.63 (SD = .56) and 2.82 (SD = .53). Compared with the Ede sample where external eating was 2.66 (SD = .54) the effect size of the differences were 0.05, and 0.29, respectively. The current scores on restrained eating in the total sample and the subsample with ages 640 years, respectively, were 2.74 (SD = .83) and 2.59 (SD = .82). Compared with the Ede sample where restrained eating was 2.21 (SD = 0.91) the effect size of the differences were 0.61and 0.41, respectively. All in all, when we compared the participants in the current subsample whose ages were similar to those in the Ede sample, we effectively replicate the earlier finding (van Strien et al., 2009) that the substantial increase in emotional eating has not been paralleled by a similar increase in external eating (see van Strien et al., 2009 for a discussion of possible explanations for this increase in emotional eating). However, it should be noted that restrained eating also showed substantial increases in the current samples.

Limitations and strengths A limitation of the current study is the use of self-reports. Participants may, for reason of social desirability, have disavowed overconsumption, emotional and external eating, or over-reported their dietary restraint. Social desirability concerns, however, are not limited to studies that rely on self-reports, because they may also affect behavior in direct tests of intake where specifically 3 Support for this explanation in the present study was found in a post hoc analysis in the subgroup of 295 high overconsumers on differences between low and high emotional eaters (median split) in frequency of intake of between-meal snacks in the past four weeks High emotional eaters admitted to having eaten high caloric between-meal snacks significantly more frequently than did low emotional eaters. Specifically, on the question How often in the past four weeks did you eat between-meal snacks such as big pieces of cake, candy bars, salty snacks, bags of crisps (response categories: never (1), almost never (2), less than once a week (3), once or twice per week (4), three of four times a week (5), five or six times a week (6), every day (7)), low emotional eaters (n = 151) had a mean response of 3.58 (SD = 1.45) whereas high emotional eaters (n = 144) had a mean response of 4.25 (SD = 1.59), t (293) = 3.902, p < .001; Cohen’s d = 0.41. A further finding in the subgroup of 295 overconsumers was that the high emotional eaters admitted to overconsume to a larger degree than did low emotional eaters. On the question on overconsumption (see Method section) low emotional eaters (n = 151) had a mean response of 6.06 (SD = .89) whereas high emotional eaters (n = 144) had a mean response of 6.45 (SD = .96), t (293) = 3.641, p < .001; Cohen’s d = 0.42.

obese people may be motivated to avoid overeating, owing to the deviant status of obesity in our culture (Krantz, 1978). Further, participants may have underestimated their body weight and overestimated their body length. However, we controlled BMI at T2 for BMI at T1, so this problem may be partly partialled out. A strength of the study is the prospective design, the large dataset, and also the fact that the data were collected in a sample of people representative of the general population of The Netherlands. Further, we were encouraged by the obese-normal weight difference in reported overconsumption, which indicated that the overweight people in the study were prepared to admit their overconsumption (an admission that may be interpreted as an indicator of self-report validity). Further, the drop-out between the assessment dates relevant to the present study was relatively low. Only 21.6% at the 2-year follow-up (T2) had missing weight and height measures, but, with the exception of age, there were no differences between the drop-outs and non-dropouts in regard to their BMI, ethnicity (Dutch versus non-Dutch), education and sex. Conclusion In conclusion, whilst increasing physical activity may attenuate weight gain, particularly high emotional eaters seem at risk for developing overweight, because overconsumption seems to be more strongly related to weight gain in people with high degrees of emotional eating. References Amenesi, J., & Whitaker, A. (2008). Relations of mood and exercise with weight loss in formerly sedentary obese women. American Journal of Health Behavior, 32, 676–683. Aphramor, L. (2010). Validity of claims made in weight management research. A narrative review of dietetic articles. Nutrition Journal, 9, 30. http://dx.doi.org/ 10.1186/1475-2891-9-30. Blundell, J., Stubbs, R. J., Golding, C., Croden, F., Alam, R., Whybrow, S., et al. (2005). Resistance and susceptibility to weight gain. Individual variability in response to a high fat diet. Physiology and Behavior, 86, 614–622. Bruch, H. (1964). Psychological aspects in overeating and obesity. Psychosomatics, 5, 269–274. CBS. Central Bureau voor de Statistiek (2009). CBS statline. . Chaput, J. P., Leblanc, C., Pérusse, L., Desprès, J. P., Bouchard, C., & Tremblay, A. (2009). Risk factors for adult overweight and obesity in the Quebec Family Study. Have we been barking up the wrong three? Obesity, 17, 1964–1970. de Lauzon-Guillain, B., Basdevant, A., Romon, M., et al. (2006). Is restrained eating a risk factor for weight gain in a general population? American Journal of Clinical Nutrition, 83, 132–138. Drapeau, V., Provincher, V., Lemieux, S., Desprès, J. P., Bouchhard, C., & Tremblay, A. (2003). Do 6-y changes in eating behaviors predict changes in body weight? Results from the Québec Family Study. International Journal of Obesity, 27, 808–814. Dunn, A., Trevedi, M., Kampert, J., Clark, C., & Chambliss, H. (2005). Exercise treatment for depression. Efficacy and dose response. Americal Journal of Preventive Medicine, 28, 1–8. Gold, P. W., & Chrousos, G. P. (2002). Organization of the stress system and its dysregulation in melancholic and atypical depression. High vs. low CRH/NE states. Molecular Psychiatry, 7, 254–275. Goldsmith, R., Joanisse, D., Gallagher, D., Pavlovich, K., Shamoon, E., & Leibel, R. (2010). Effects of experimental weight perturbation on skeletal work efficiency, fuel utilization, and biochemistry in human subjects. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology, 298, R79–R88. Haskell, W. L., Lee, I. M., Pate, R. R., Powell, K. E., Blair, S. N., Franklin, B. A., et al. (2007). Updated recommendation for adults. From the American college of sports, medicine and the American heart association. Circulation, 116, 1081–1093. Herman, C. P., & Polivy, J. (2008). External cues in the control of food intake in humans. The sensory-normative distinction. Physiology and Behavior, 94, 722–728. Herman, C. P., van Strien, T., & Polivy, J. (2008). Undereating or eliminating overeating? American Psychologist, 63, 202–203. Holmbeck, G. N. (2002). Post-hoc probing of significant moderational and mediational effects in studies of pediatric populations. Journal of Pediatric Psychology, 27, 87–96. Holmes, M. E., Ekkekakis, P., & Eisenmann, J. C. (2010). The physical activity, stress and metabolic syndrome triangle. A guide to unfamiliar territory for the obesity researcher. Obesity Reviews, 11, 492–507.

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